(515g) Intermittent Desorption-Mediated Surface Diffusion

The mobility of molecules on a solid surface plays a key role in diverse phenomena such as friction and self-assembly and in surface-based technologies like heterogeneous catalysis and molecular targeting.  To understand and control these surface processes, a universally applicable model of surface transport at solid-liquid interfaces is needed.  However, unlike diffusion at a solid-gas interface, little is known about the mechanisms of diffusion at a solid-liquid interface.  Using single molecule tracking at a solid-liquid interface, we found that a diverse set of molecules, including polymers and proteins, underwent intermittent random walks with non-Gaussian displacements.  This contrasts with the normal random walk and Gaussian statistics that are commonly assumed for molecular surface diffusion.  The molecules became temporarily immobilized for random waiting times between surface displacements produced by excursions through the bulk fluid.  We propose that intermittent hopping is universal to molecular surface diffusion at a solid-liquid interface.